Beam structure



A. P. LUNDIN. BE AM STRUCTURE. APPLICATION FILE D DEC. 7. I920 INVENTOR PatentedSept 19,1922. 7

Patented Sept. 19,1922.

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ANDREAS r. L'UNDIN, or rLnsnme,'uEw'Yonx, assIoRon-n'o i company, mo, A conrona'rron or new YO.

IBEAM STRUCTURE.

Original application filed November To all whom it may concern: 7

Be it known'that I, ANDREAS P. LUNDIN, a citizen of the United-States, and a resident of Flushing, borough of Queens, county of Queens, and State of New York, have invented certain new and useful Improvements in Beam Structures, of which the following is a specification.

This invention relates to improvements in beam structures, and is especially adapted for use in aerofoil frames and like aircraft structures and is a division of the subject matter included in my application, Serial parably the lightest material procurable but also possesses comparatively great strength, and furthermore possesses the additional characteristics of sound and heat insulation.

This material, however, is porous, soft, pithy and easily fracturable and does not itself ossess the necessary ualities to enable aerooil ribs to be manu actured of this wood alone. I have found, however, when a body or trunk portion of this material is faced or flanked with layers or plates of a hard and tenacious material, such as compressed or indurated fibre or composition which is securely fastened to the trunk over its entire surface, so as, in efiect, to make said trunk and layer or layers of tough material a single integral structural body, a composite material is produced which possesses in a high degree the qualities sought in structural materials for aircraft manufacture and is very desirable for use in aerofoil ribs and like aircraft frame-construction. Such composite material will have ample strength, suitable flexibility and will be of much less weight in proportion to strength than is inherent in the wooden ribs and like aircraft frame parts now employed in airplane construction. In fact, I find that a rib so produced has greater.

advantages of structure and stre h thanis inherent in a beam of s1m1larimens ons wholly composed ofindurated fibre mira e ier material though possessing mucli gless weight. I also find that the tenacity and e1, 1918, Serial 350. 263,484. mama and this application filed Decemher 7, 1920. Serial No. 429,043.

elasticity of a rib or like element made of such composite material are respectively very much reater than the sums. of the ten'acltles an elasticities of the component partsor materials and also eater than the tenac1t1 es and elasticities o ribs of simila dimensions composed of the heavier material whlle it is, of course,- weight.

Such material is, in efiect, an I-beam and from an engineering standpoint nustbe 'figured 1n the same manner assucli beams and theouter tough layers of fibre will act similarly to the flanges of an I-beam while the balsa wood trunk or body will act similarly to the web of such a beam; that is to say, the strength of the complete structure is caused very much lighter in" to betransferred toward the said outer tough layers. or flanges and the body or web of balsa wood,. not only forms the major part of I the composlte material so as to afford ex-' treme lightness in weight, but also transmits stresses toward the outer portions of the said material, and as aforesaid it combines in one integral structure the desirable characteristics of great structural strength, extreme lightnessand weight, resistance to strains of compress1on, crus ing, shearing and torsion, as well as surface hardness. Furthermore any local strain applied at the hard surface or surfaces will be caused to be distributed over a considerable area adjacent to the place of application of the stress or pressure caus- 111g such local strain.

In my preferred form of aerofoil' ribs and spars the web of the rib is composed of this composite material of my invention, and said web preferably has struts and interstruts openings of suitable dimensions cut therein to further eliminate weight. I also prefer to make the top and bottom longitudinally-extending portions of such rib of a suitable tough material or" wood such as fibre or' spruce.

Balsa wood and similar light woods readily absorb water and therefore such woods employed by me in aircraft;- construction are treated by the use of para'fli'n to preserve and make the s'amewater roof.

With these and ot er objects in view, the invention comprises the combination of members and arrangement of parts so combined as to co-act and cooperate with each other in the performance of the functions and the ac complishment of the results herein content plated, and comprises in one of its adapta= tions the species or preferred form illustrated in the accompanying drawings, in which v Fig. l is a plan view of a piece'of material suitable for use in aircraft construction as the web of a rib for aerofoil frames;

Fig. 2 is a side elevation of a rib embody ing my invention;

F Fig. 3 is a section on the line 3-3 of d is an enlarged detail edge View of a fragment of balsa wood board before the layers or flanking plates are applied;

Fig. 5 is a similar View with the side layers applied; and

ig. 6 is another similar view illustrating the composite board impregnated with paraffin to waterproof and preserve the same.

Referring now to these drawings, 1 (Fig.

'1) indicates a composite. board or beam suitable for use when properly shaped as the web portion of a rib 2, (Figs. 2 and 3) suitable for use in aerofoil frames. In these figures, the web portion 1 of the rib 2 comprises, as aforesaid, a composite board embodying a body or trunk 3 of balsa wood or the like, on the opposite surfaces of which are mounted layers, skins or flanking plates 4 and 5 of tough fiber such as compressed or indurated fiber, such layers be-' mg preferably glued securely tothe outer surfaces of the said balsa wood body before the web is cut as hereinafter stated. Part of the said web is preferably cut away to further eliminate weight and to provide upper and lower rim strips 6 and 7; struts 8 merging with such rim strips and interstrut openings 9. In the construction of the web the trunk is preferably of a width similar to that of the layers 4: and 5, as illustrated in Figs. 2. and 3.

Also as illustrated in said Fig. 3, the web 2 is, as shown, preferably fitted into notches 10 in top and bottom flanges 13 and 14:, and the top and bottom edges of the web are preferably securely glued to the said flanges which are preferably composed of hard wood, fiber or other suitable material. I thus produce a rib of extreme lightness and great strength.

The said web 1 is as aforesaid formed of an inner bod or trunk and outer layers, skins or flan ing plates at opposite sides thereof, and as illustrated more particularly in Figs. 4, 5 and 6, the said trunk provides the main or basic structural element of the web. Because this body or trunk is composed of balsa wood or similar extremely light, soft, porous or easily fracturable wood, such as ceiba, it possesses the desirable characteristics of lightness in weight, sound insulation and heat insulation and has as a whole a maximum of structural menace strength relative to its, weight and also has relatively great resistance to strains of compression and torsion but it is, as aforesaid, relatively soft, porous and pithy in structure and offers but little resistance to local fracture or depression. When the outer surface layers, skins or flanking plates 5 and 6 which are composed of a hard and tenawood core or'trun-k may be first treated and the outerlayers or flanking plates subsequently applied or the said outer layers or plates may be first applied and the complete element then. treated as indicated in Figs. 4, 5 and 6, in which the dark and close .broken lines are intended to indicate impregnated wood.

By the use of a web of this character, it

am enabled to produce a beam structure which may be used as an aerofoil rib which as a whole or complete structure will combine great strength and resistance to strains ofcompression or torsion and also by reason of the hardness and resistance to fracture, crushing and shearing of its-surface or surfaces, any local strains applied on such hard surfaces will be caused to be distributed over a considerable area adjacent to the point of application of the stress causing the local strain.

. The tenacit and elasticity of such a web are respective y very much greater than the sums of the tenacitiesand elasticities of the component parts of materials and also greater than the tenacities and elasticities of a. beam of similar dimensions composed of the heavier material while it is of course very much lighter in weight. Said strum ture is in effect an 1l-beam and must be figuned in the same manner as an l-beam. In other words tough-fiber layers will act,similarly to the flanges of an ll-beam and the balsa wood trunk will act similarly to the web of an ll-beam, that is to say, the strength of the structure is caused to be transferred toward the tough outer layers or flanges and thetrunk or body of balsa wood therefore not only forms a major part of the composite structure, thus lending its characteristic of lightness thereto, but also trans= mits stresses toward the said outer portions.- The use of my composite boards, therefore,'in the construction of an airplane rib its use

neaaeoo employed inaerofoil frames but will have the desirable characteristics above described. Having described my invention I claim 1. An airplane frame, the Structure of which consists in part of balsa wood, suitabl treated with paraffin to preserve it and ma e it waterproof and flanked by plates of relatively tough material.

2. An airplane frame, the structure of which consists in part of balsa woodflanked by plates of relatively tough material.

3. An airplane f frame, the structure of which consists in rt of balsa wood flanked by plates of toug fiber. g

4. An aerofoil ribwhose webiconsists of a board composed of balsa wood flanked by plates of relatively tougher material. 1

5. An aerofoil rib whose web consists of a board composed of balsa wood flanked by plates of tough fiber.

6. A rib for aerofoil frames embodyin hardwood top and bottom flanges and a we comprising a composite beam composed of" a central trunk of balsa wood and relatively thin outer layers of'a hard and tenacious material on opposite'sides of and securely. fastened to said trunk, said web being-cut out to provide rim strips, struts merging with said rim strips and inter-strut openings therebetween.

7. A beam structure composed of oppositely disposed layers of a suitable tough material possessing surface hardness and an' intermediate trunk of balsa wood suitably treated with a preservative material, said trunkand outer layersbei'ng securely fastened together to form, a substantially integral structure. v ,-f

'8. A beam structure composed of a trunk of wood having substantially the qualities of balsa'wood, and a surface layer of hard and tenacious material securely fastened thereto, whereby a composite beam is produced in which any local strain applied at the said surface layer will be distributed on the beam as a whole over a considerable area from the point of application of the stress causin such strain, and the complete structure will possess the desirable characteristiw of elasticity and lightness in weight combined with tenacity, structural strength and hardness of surface;

In witness whereof, I have signed my name-to the foregoing specification in the presence of two subscriblng witnesses.-

ANDREAS P LUNDINL W t se f I Wnmnmw, STALLo'VmroN. 

